Fig. 3: Regulation of transcription of the σ70 controlled Suf system.
From: The route to transcription initiation determines the mode of transcriptional bursting in E. coli
The Suf system enables the assembly of Fe-S clusters of bacteria under oxidative stress and iron limitation28,29,40,41,42,43. Under reducing and iron replete conditions, transcription from the Suf promoter is repressed by Fur[Fe2+], preventing access of RNA polymerase/σ70 and the activator IscR to the promoter. The reduced form of the activator OxyR under these conditions has low affinity for the promoter. Under oxidising and iron deplete conditions (e.g. in presence of H2O2 and bipyridyl, BP), the oxidsed form of OxyR[S-S] and the Apo form of IscR have higher affinity for the promoter than the oxidised and/or Apo form of Fur. Integration Host Factor (IHF) bends the promoter DNA bringing OxyR[S-S] and RNA polymerase/σ70 into close contact. OxyR[S-S] and the Apo form of IscR stabilise the contact of RNA polymerase/σ70 with the promoter resulting in transcription.
